Vol. I · A Postgres HandbookTwelve chapters · · 756 queries

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

IntermediateBasic SELECT

Constraint Practice: Add CHECK constraint variant #3

SQL

ALTER TABLE practice_table_3
ADD CONSTRAINT chk_data_3 CHECK (LENGTH(data_value) > 3);

Tested against PostgreSQL 16

Note

“Ensuring data integrity through check constraints (Pattern #3).